Really needs a better name. The Species Survival Person is something like a Cosmic Keystone to a single species or race of beings. As long as they live, all existing members of that group can live, and new ones can be born or made. Should the Species Survival Person be killed or die, then either a massive attack of No Ontological Inertia will hit and all the group will die, or their ability to procreate will be removed and lead to eventual extinction. It takes more to be a Species Survival Person than mere knowledge of how to manufacture more Mecha-Mooks or genetically engineer more mutants or Plant People or what-not. To be a Species Survival Person requires that the individual in question's very existence be necessary for the group's survival, though not necessarily that they be able to procreate/build more of the group. One possibility is that they are a Power Source (or Curse source) for all the group, typically the case with vampires, and removing them makes all the group either revert to human, burst into dust, or shut down. Another possibility is that they are The Maker and/or only one who can procreate. If evil, they're frequently the Big Bad and killing them will decapitate the Keystone Army. If good (or at least neutral) they represent a high Uniqueness Value for what they can do. The queen of a race of Bee People can often serve this role (provided there are no other queens).
- In Dance in the Vampire Bund, the Mina Tepesh (descended from that Tepesh) is this for the vampire race. However, as long as a carrier of the pure-blood legacy (un)lives, the species is safe, which comes into play since there is pressure on her to bear an heir.
- Underworld had this trope invoked by Markus, sire of all vampire kind, who played it as a means to keep both himself safe from underlings and his werewolf brother from being killed.
- In Lost Boys the head vampire is this to anyone down their bloodline, those who aren't full vampires revert back to humans.
Hello, Unknown Troper. You'll need to get known to lend a hand here.